Reverse lay strand



y 16, 1967 R. E. CORRALL ETAL 3,320,350

REVERSE LAY STRAND Original Filed July 2, 1962 5 Sheets-Sheet 1 INVENTORJ ROY E. CORRALL GEORGE N. MENASOF F May 16, 1967 R. E CORRALL ETAL 3,320,350

REVERSE LAY STRAND 5 Sheets-Sheet 2 Original Filed July 2, 1962 ML mu 3 V mm E. Y o R GEORGE N. MENASOFF' [III/0 Mil/I May 16, 1967 R. E. CORRALL ETAL REVERSE LAY STRAND 3 Sheets-Sheet 5 Original Filed July 2, 1962 INVENTORY ROY E. CQRRALL GEORGE N. MENASOFF Mz/M United States Patent Ofifice 3,320,350 Patented May 16, 1967 LAY STRAND Roy E. Corrall, Franklin Square, and George N. Menasofl, iarryttwvn, N.Y., assignors, by mesne assignments, to Anaconda Wire and Cable ompany, a corporation of Delaware Original application .iuly 2, 1962, Ser. No. 206,764, new Patent No. 3,169,360, dated Feb. 16, 1965. Divided and this application Aug. 24, 1964, Ser. No. 395,639 13 Claims. (Cl. 174-34) This is a division of application Ser. No. 206,764, filed July 2, 1962, now Patent No. 3,169,360.

Our invention relates to strand twisting and particularly to the twisting of strand with a false or reversing twist.

In the stranding of insulated conductors there are certain advantages to twisting the strands in a false twist with periodic reversals of direction of lay rather than twisting them in a continuous helix in the manner most commonly practiced. Among these advantages are the facts that in applying a false twist it is not necessary to rotate the take-up or pay-off assembly and the expensive equipment necessary for the rotation of heavy reels can be eliminated. With the elimination of heavy rotating elements comes the additional advantage of increased speed of operation. There are also advantages in the false twisted product itself in that slack can be generated in short lengths of such starnd merely by untwisting a central length of it even when the ends are remote, without any necessity for cutting the conductors. A most important advantage, however, from the vantage point of this invention, is that when strands are twisted with a false twist the stranding operation can be part of a continuous process involving steps both downstream and upstream of the twisting where the ends of the strand are not available for rotating. Such a process would occur for instance where conductors are insulated in an extruder, twisted into pairs, and combined to form a cable. In contra-distinction to such a proposed process it is present commercial practice to insulate conductors individually and take them up on reels. The insulated conductors on two of the reels are then twisted into pairs and taken up on reels again. Finally the pairs of a plurality of these reels are stranded into a cable. It has been known to apply a false twist by) passing filaments through a reciprocating lay plate but the angle of such twists has been limited to a fraction of a full turn because of the tangling of strands upstream of the lay plate and in no case has been able to exceed 540".

We have invented apparatus applying a reversing twist to advancing strand comprising means accumulating such strand which may be, but is not necessarily limited to, a sheave, a roll supporting a plurality of turns or a pair of rolls supporting at least one loop and mounted in a cradle, and also comprising means for rotating the accumulating means, such as by rotating the cradle, so as to impart a twist of one direction to the strand leaving the accumulating means, and a twist of opposite direction to the strand entering the accumulating means. Our apparatus also comprises means for alternately restraining the accumulating means against rotating for a period sufiicient to advance the twisted strand from it, and may also comprise means for binding the strand, preferably at reversal points while leaving the strand free from binding elsewhere. Such binding may be quick-setting cement such as but not limited to the hot-melt adhesive such as that described in application Ser. No. 190,108, filed Apr. 25, 1962, and assigned to the assignee of this invention.

Where reverse-lay or false twisting has been used for the stranding of prior art electric cables it has not been known to twist more than a fraction of a turn between reversals. We have invented reverse twist cables with angles of twist in excess of 546 and even in excess of three or more complete turns. These may be but are not limited to telephone conductor pairs of two insulated wires or multi-pair cables comprising a plurality of such twisted pairs with a jacket overall. Our cables may be made with reverse twisting of the strands, and binding at the points of reversal, the strands being free from binding elsewhere along their lengths; and the bind ing may be a hot-melt adhesive.

We have also invented a method of twisting a strand comprising continuously advancing it into an accumulated supply of strand while simultaneously paying the strand from the supply and periodically rotating the supply to impart a twist to the strand leaving the supply, and an opposite twist to the strand entering the supply. In our method the supply is preferably alternately restrained against the rotating or rotated in the opposite direction until the twisted strand has paid from it and the angle of rotation is in excess of 540 and preferably encompasses a plurality of full turns. Our method also preferably comprises the step of binding the strand intermittently at reversal points as by a hot-melt adhesive, which binding may advantageously occur as the first step in our process. A more thorough understanding of our invention can be obtained from a study of the appended drawing.

In the drawing:

FIGURES 1a and 1b are perspective views of an apparatus made to our invention.

FIGURE 2 is a perspective view of an adhesive applicator used in one embodiment of our invention.

FIGURE 3 is a lengthwise View of a twisted strand of our invention.

FIGURE 4 is a lengthwise, cut-away View of a cable of strands of our invention.

Referring to FIGURES 1a and 1b a stranding ap' paratus, indicated generally by the numeral 10 is mounted on a base 11. A strand 12 comprised of parallel insulated conductors 13, 14 is advancing from right to left as seen in the drawing from a supply source not shown. One apparatus has particular utility for the twisting of telephone cable pairs such as may be made from the insulated conductors 13, 14 but it can also be advantageously used for quads and for other types of strand comprising a greater or fewer number of conductors or other filaments. The strand 12 passes through a bind ing head 16 where it is bound together at fixed intervals along its length. We have shown a known type of commerically available binding head of which the Wire and Harness Taper made by the Possis Machine Corp., 825 Rhode Island Avenue, Minneapolis 26, Minn. is an eX- ample. In this embodiment of the binding head 16 a gummed tape 17 feeds from a pad 18 and a short length of the tape is automatically wrapped around the strand at selected intervals. Since our strand 12 is continuously advancing we have mounted the binding head 16 on rails 19 so that it can be advanced at the speed of ad vancement of the strand 12 by the rotation of a worm 21 driven by a reversing motor 22. After the strand 12 has been bound at one point the motor 22 reverses to turn the worm 21 in the opposite direction so that the head 16 is returned to its original position. This is quite feasible in our apparatus because the long length of strand between reversal points allows ample time for the returns of the head 16, and it constitutes one of the advantages of our invention. Although we have shown a binding head 16 which wraps gummed tape around the strand it will be readily understood that we do not wish to be limited to this method of binding. For instance, in FIGURE 2, we have shown a binding means hereinafter to be explained in detail, which utilizes hot-melt or other quick-setting adhesive for binding our strand 12. As the strand pays from the binding head 16 is passes through a hollow journal 23 which turns in a bearing 24 mounted on a pedestal 26, which is in turn supported on the base 11. Also mounted on the base 11 another pedestal 27 is surmounted by a hearing 28 in which another hollow journal 29 rotates in line with the journal 23. The journals 23, 29 support between them a cradle 31, which we prefer to form from a single bar 32 for ease in stringing, as shall be shown. The bar 32 mounts an upper rigid bearing 33 which supports a grooved roll 34 on a cantilevered shaft 36. The roll 34 is wide enough to contain a plurality of grooves 37 and it will be understood the greater the number of grooves 37, other factors being equal, the greater will be the storage capacity of our apparatus. It is, however, contemplated that for some applications the roll 34 may have a single groove and take the form of a simple sheave. Upstream and to the right of the hearing 33, a bearing 38 is mounted on the underside of the bar 32. The bearing 38 supports a light-weight flanged roll 39 on a cantilevered shaft 41. The roll 39 is wide enough to accommodate all the turns of strand supported by the grooves 37 and the strand is formed in a plurality of loops 42 enclosing the two rolls 34, 39. The rolls 34 and 39 are of very light-weight construction so that they are easily turned by the forward motion of the strand 12 but it will be understood that where the strand might be broken or damaged by the load incurred in turning them, the rolls 34 and 39 may be driven by gear trains or other means known to persons skilled in mechanical arts.

Before entering upon the roll 39 the strand 12 passes through a pair of pinch rolls 43, 44 mounted on a bar 46 fixed to the base 11 by means of a pedestal 47. Thus the pinch rolls 43, 44 remain stationary and do not rotate along with the cradle 31 and are tight enough to prevent back twist in the strand 12. In the embodiment of our apparatus shown in FIGURES 1a and 1b the strand 12 makes one turn around the roll 39 adjacent to the near flange, and then passes around the grooved roll 34 and back to the roll 39 to form the series of loops 42. Leaving the roll 34 the strand passes over guide sheaves 48, 49 through another pair of pinch rolls 51, 52 and thence to take-up means not shown, which may incorporate another processing step. The pinch rolls 51, 52 are fixed to a bar 53 rigidly mounted to the base 11 by means of a pedestal 54. A belt pulley 56 is locked to the journal 23 and is driven through a belt 57 by means of a drive pulley 58 and motor 59 which we prefer to be a high-inertia rotor motor. The pulley 58 is connected to a shaft 61 of the motor 59 through a clutch 62 and can be stopped by an electric brake 63. The clutch 62 and brake 63 are actuated by a limit switch 64 through brushes 66, 67 and slip rings 68, 69. The limit switch 64 is, in turn, actuated by a cam 71 driven at a selected reduction ratio from the roll 39. In the apparatus shown we prefer to employ a reduction ratio of 20 to 1, operating in a known manner so that the drive pulley 58 will be stopped by the disconnection of the clutch 62 and application of the brake 63 after twenty revolutions of the roll 39, and will start again after another twenty revolutions, and so on. Thus the cradle 31 is caused to rotate for a period equal to twenty revolutions of the roll 39 and alternately to remain stationary for twenty revolutions. In this regard it should be particularly noted that in one method of operation of our apparatus the rolls 34 and 39 rotate continuously at a constant rate and the motor 59 runs continuously in the same direction; the cradle 31, although it stops and starts at regular intervals does not reverse its direction of rotation but rotates always in the same direction. In another method of operation the clutch 62 is a reversing clutch and the cradle 31 rotates alternately for twenty revolutions clockwise and counterclockwise.

A second limit switch 72 is connected through slip rings 73, 74 and brushes 76, 77 and wires 78, 79 therefrom to the binding head 16 so that the binding head applies binding to the strand once for every. twenty revolutions of the roll 39. The switch 72 is actuated by a cam 75 driven by a reducing mechanism from the roll 39. The earns 71 and 75 turn at equal rates of speed but are out of phase to an extent selected so that a bound point in the strand 12 reaches the pinch rolls 43, 44 each time the rotation of the cradle 31 stops or starts.

It will be understood that although we have selected a length of twenty circumferences of the roll 39 as the length of strand between reversal points other lengths can also be chosen within the scope of our invention, but the length should correspond to the length of strand stored on the rotating cradle 31 between the pairs of pinch rolls 43, 44 and 51, 52. In the illustrated case this length is just twenty circumferences of the roll 39.

Although we have preferred to apply binding to our strand 12 upstream of its entrance into the storage rotating means our invention also will include apparatus where the binding head is mounted downstream of the cradle and applies binding to strand emerging from the pinch rolls 51, 52. Such a binding might be applied continuously as by winding with a yarn or tape, or it might be applied only at points of reversal. The extent of binding required depends to some extent on the springiness of the strand being twisted. We have found that polyethylene-insulated, solid-copper telephone conductor pairs can be twisted very satisfactorily on the apparatus described and shown in FIGURES 1a and 1b. Where the springiness of the strand is such that the false twist tends strongly to unwind under very slight tension this unwinding might take place in the unsupported portions of the loops 42 between the rolls 34 and 39. This can be overcome at the expense of storage capacity by having only a single roll such as the roll 39 mounted on the cradle 31 so that the stored strand will, at all times, be restrained from unwinding by its frictional contact with the surface of the roll. If the strand is then bound continuously as it leaves the cradle, even a springy strand will retain its false twist.

OPERATION To operate the apparatus of FIGURES 1a and 1b a pair, or other plurality of filaments making up the strand 12, are threaded through the binding head 16, journal 23, and pinch rolls 43, 44. The strand 12 is wrapped for one turn around the roll 39 and then looped around the grooves 37 in the roll 34 and also the roll 39 until all the grooves 37 have been used. This stringing of the strand 12 is greatly simplified by the cantilever mounting of the rolls 34 and 39. The threading of the strand continues over the sheave 48 and under the sheave 49, through the final rolls 51, 52 and downstream to the take-up apparatus, not shown. It will be understood that, in order to avoid waste, all or part of this threading may employ a piece of scrap lead-cord that can be discarded later.

The motor 59 is operated with the clutch 62 engaged and the brake 63 released so that the cradle 31 rotates as the strand 12 pays through the apparatus. As the cradle rotates it applies a twist to the strand 12 at the pinch rolls 51, 52 so that the strand advancing downstream of the apparatus is twisted. At the same time, the strand 12 entering the apparatus through the pinch rolls 43, 44 is given a twist in the opposite direction to the twist imparted by the pinch rolls 51, 52. As the stranding progresses the untwisted strand that was initially stored t) on the rolls 34, 39 is twisted as it pays off through the pinch rolls 51, 52 while the fresh strand being taken up in the storage is twisted at the rolls 43, 44 and stored in the twisted condition. When twenty circumferences of the roll 39 have been paid into the apparatus all the untwisted strand will have advanced from the storage and will have been replaced by twisted strand. At this point the cam 71 will actuate the switch 64 to disengage the clutch 62 and apply the brake 63 thus stopping rotation of the cradle 31. However, the strand 12 will continue to pay through the pinch rolls 51, 52, but since all the stored strand is twisted in a direction opposite to the strand already advanced there will be a point of reversal in the strand passing through the rolls 51, 52 at the time the cradle stops rotating. As the twisted strand continues to advance from the stationary cradle it is replaced by untwisted strand passing through the rolls 43, 44. When the twisted strand is completely replaced by untwisted strand the clutch 62 will engage and the cradle will start to rotate and thus repeat the cycle. During this operation the binder head 16 is applying a gumn1ed-tape binding to points of the strand which correspond to points of reversal of twist with the result that the false twist does not unwind when the strand emerges from the apparatus. When, instead of remaining stationary at the end of each cycle, the cradle 31 rotates alternately clockwise and counterclockwise, the strand taken up in the storage is always twisted and an additional twist in the same direction is applied to the strand as it leaves the storage.

Duringthe initial loading of the storage with twisted strand (and during each of the subsequent periods between reversal points) the cradle will make a plurality of complete revolutions: For example, if the length of twistl-ay is six inches and the circumference of the roll 31 is one foot there will be forty full turns in the strand between reversal points. This large number of turns has a number of important advantages. For one thing it reduces the number of bindings required where the bindings are applied only at reversals. It provides ample time for the return of the binding head. It prevents the false twist being unwound by tension in the strand. And it reduces the frequency of starting and stopping of rotation of the cradle.

In a preferred embodiment of our invention, binding of the strand is accomplished by an apparatus 100 shown in FIGURE 2. In this apparatus the conductors 13, 14 pass through respective separating guide blocks 101, 102 mounted on a platform 103 on a pedestal 104 on the base 11. Also mounted on the platform 103 is a solenoidcontrolled nozzle 105 to which is supplied a suitable hotmelt, or other quick-setting cement such as that hereinbefore described through an insulated pipe-line 106 from a source not shown. The nozzle 105 is activated by the switch 72 through the lead wires 78, 79 to apply a deposit of cement to the wire 14 at points corresponding to points of reversal of the twist, immediately after which, the condoctors 13, 14 pass between grooved pinch rolls 107, 108 where they are brought together and bound by the cement. From the rolls 107, 108 the strand passes through the hollow journal 23 and is processed as hereinbefore described.

The length of the conductor 14 to which cement can be continuously applied by this method is not limited and this provides for some latitude in obtaining perfect registration between the point of binding and the point of reversal of twist. Alternatively, it is within the scope of our invention to mount the apparatus 100 downstream of the cradle 31 to bind the strand after it has been twisted.

In FIGURE 3 we have shown a paired strand 110 twisted in accordance with our invention. The strand is comprised of insulated conductors 113 and 114 which can be seen to have a right-hand twist at a length 116 and a left-hand twist at a length 117. Reversal points occur 6 at 118, 119, 121 and in between these reversals the twist in the strand continues in one direction for a large plurality of turns. At the reversal points bindings 122, 123, 124, which consist in this embodiment of hot-melt adhesive, prevent the strand from opening. Although we have shown binding only at reversal points it might be continued for a longer distance within the scope of our invention, and instead of a hot-melt cement might consist of other adhesive means, or' of wraps of adhesive tape or continuous servings of yarn or tape.

In FIGURE 4 a plurality of the paired strands have been formed into a cable 126 with a jacket 127.

We have invented anew and useful apparatus and method and products formed thereby for which we desire an award of Letters Patent.

We claim:

1. An electric cable comprising:

(A) a plurality of insulated conductors twisted with a reversing direction of lay having periodic points of reversal,

(B) binding applied to said cable at said points,

(C) said cable being free from said binding elsewhere along its length.

2. The cable of claim 1 wherein said binding is a quicksetting adhesive.

3. An electric cable comprising:

(A) a plurality of insulated conductors twisted with a reversing direction of lay having periodic points of reversal,

(B) the angle of twist between said points being in excess of 540,

(C) binding applied to said cable at said points,

(D) said cable being free from said binding elsewhere along its length.

4. The cable of claim 3 wherein said binding is a quicksetting adhesive.

5. A telephone conductor pair comprising:

(A) two insulated wires twisted with a reversing direction of lay having periodic points of reversal,

(B) binding applied to said pair at said points,

(C) said pair being free from any binding elsewhere along its length.

6. The pair of claim 5 wherein said binding is a quicksetting adhesive.

7. A telephone conductor pair comprising:

(A) two insulated wires twisted with a reversing direction of lay having periodic points of reversal,

(B) the angle of twist between said points being in excess of 540,

(C) binding applied to said pair at said points,

(D) said pair being free from said binding elsewhere along its length.

8. The pair of claim 7 wherein said binding is a quicksetting adhesive.

9. A multi-pair cable comprising:

(A) a plurality of pairs of insulated wires,

(a) said pairs each being twisted with a reversing direction of lay having periodic points of reversal,

(b) said pairs comprising binding applied at said points,

(c) said pairs being free from binding elsewhere along their lengths, and

(B) a jacket over said cable.

10. The cable of claim 9 wherein said binding is a quick-setting adhesive.

11. A multi-pair communication cable comprising:

(A) a plurality of pairs of insulated wires,

(a) said pairs each being twisted with a reversing direction of lay having periodic points of reversal,

(b) the angle of twist between reversals being in excess of 540,

(c) said pairs comprising binding applied at said points,

7 ((1) said pairs being free from said binding elsewhere along their lengths, and (B) a jacket over said cable. 12. The cable of claim 11 wherein said binding is a quick-setting adhesive.

13. A multi-pair communication cable comprising: (A) a plurality of pairs of insulated wires,

(a) said pairs each being twisted with a reversing direction of lay having periodic points of reversal,

(b) the angle of twist between reversals being a plurality of full turns,

('0) said pairs comprising binding applied at said points,

(d) said pairs being free from said binding elsewhere along their lengths, and (B) a jacket over said cable.

References Cited by the Examiner UNITED STATES PATENTS 491,109 2/1893 Holman 17434 7 2,790,299 4/1957 Gillis et 'al. 57-64 X 3,025,656 3/1962 Cook 57156 X 3,052,079 9/1962 Henning 57156 X LEWIS H. MYERS, Primary Examiner.

L. E. ASKIN, H. HUBERFELD, Assistant Examiners. 

1. AN ELECTRIC CABLE COMPRISING: (A) A PLURALITY OF INSULATED CONDUCTORS TWISTED WITH A REVERSING DIRECTION OF LAY HAVING PERIODIC POINTS OF REVERSAL, (B) BINDING APPLIED TO SAID CABLE AT SAID POINTS, (C) SAID CABLE BEING FREE FROM SAID BINDING ELSEWHERE ALONG ITS LENGTH. 